The present invention relates to composite panel doors and, more particularly, to a hinge assembly used to mount the door within a frame, as well as a method of securing the hinge assembly to the door.
Medium density fiberboard is a composite panel product that typically comprises lignocellulosic fibers combined with a synthetic resin or other suitable bonding systems under heat and pressure. Four standard grades of medium density fiberboard are commercially available in North America and are classified under ANSI Standard A208.2 based on product density and other physical and mechanical properties.
Medium density fiberboard is widely used in the manufacture of furniture products because it provides a flat, smooth surface that can be precisely machined and easily finished. The use of medium density fiberboard for cabinet and passage doors is particularly desirable because of its smoothness, insulating properties and resistance to warping. One problem associated with doors constructed from medium density fiberboard is that the screw holding capacity of the fiberboard material may be less than desired in many applications. As a result, manufacturers recommend that specially sized pilot holes be used and that single thread parallel core screws be used in place of traditional wood screws to secure the hinges to the fiberboard material. These special requirements may present problems for installers who are unaware of the requirements or who do not have access to the recommended type of specialty screws in a finish that matches the hinge.
An alternative to the use of specialty screws to mount the hinges directly to the medium density fiberboard material is the use of wood edge banding along at least the hinge side of the door to present a wood surface which can securely retain conventional wood screws and provide the strength needed to withstand the loads experienced by the hinges. Edge banding, however, can add significantly to the cost of the door because of the need for additional equipment, material and production steps to install the edge banding. The joint between the edge banding and the fiberboard core material is aesthetically undesirable and often requires the use of a panel known as a "crossband" which extends from top to bottom and from side to side on the door to hide the edge banding joint and prevent it from "telegraphing" through the overlying veneer. The crossband further adds to the cost of the door and does not always completely hide the underlying joint.
Another approach to improving the screw holding capability of composite panel doors involves the use of a wedge-shaped strip of wood which is inserted into a groove cut from the top to bottom of the door along the hinge side of the door. Because the groove is formed only in the side of the door, no joint is formed along either face of the door and the use of a crossband is unnecessary. There is still, however, the problem of telegraphing of the joint along the side of the door when a veneer or other coating is applied to the door. The wedge-shaped wood may have different moisture absorption properties than the core material and may cause warping of the door.
A need thus exist for a method and apparatus to increase the screw holding and hinge loading capacity of a composite panel door without causing the disadvantages resulting from conventional approaches.